This invention relates generally to a torquing device. More particularly, this invention relates to an improved ratchet mechanism for a powered wrench.
The wrench of the type to which the present invention applies includes an oscillating power unit adapted to provide torque to a socket assembly during each forward stroke, and a ratchet mechanism which permits the drive mechanism to return to its initial position at the completion of each stroke without applying a reverse torque to the socket assembly. The wrench is designed to distribute the load of the power source evenly to the socket by causing two or more coupling elements of the ratchet to assume an equal share of the applied load. The wrench comprises a socket member and a drive unit having complimentary recess formed on the adjacent faces thereof. Coupling elements, which may take the form of cylindrical pins, are located in the recesses, and a garter spring or "O" ring or similar element is disposed in the unit and serve to urge the coupling pins toward the recess surfaces of the socket unit. Each recess of the driving unit, its associated recess on the socket member and the associated coupling member defines a coupling and/or ratchet unit. The combined coupled and/or ratchet unit form the ratchet assembly for the wrench. During operation, the driving unit is moved in one direction, two or more of the pins are seated in recesses in the socket member and are trapped between surfaces of the recesses of the drive unit and the socket member to couple the socket member to the drive unit and thereby rotate the socket member. When the drive unit is rotated in the opposite direction, the pins are moved out of driving engagement between the drive unit and the socket member, thereby uncoupling the socket and drive unit so as to permit the free return of the drive unit without causing a corresponding rotation of the socket member. During this return stroke, the pins are carried with the drive unit and move from one recess site toward the next recess site where two or more pins are again seated in recesses of the socket member in anticipation of another power stroke.
Hydraulically powered wrenches of the general type discussed above are marketed by the Powerdyne Division of Raymond Engineering Inc., and an early version of one type of such wrench is shown in U.S. Pat. No. 3,745,858, particularly FIG. 6 thereof. U.S. Pat. No. 3,745,858 is owned by the assignee of this invention, and it is incorporated herein by reference in its entirety.
While suitable for it's intended purposes, the wrenches described above, and particularly the ratchet assembly thereof, suffer from one particular deficiency or drawback, which is that the pins may not move properly in synchronism between recess sites of the socket member. The problem does not occur if the pins are always driven only through the trailing edge of the drive unit recess, because movement of the pins is then always synchronized. The problem that arises, is that a pin may move in advance of the trailing edge of the drive unit recess. For example, due to foreign matter, e.g., dirt, or flaking of material lodging between the pins and the garter spring or due to lack of proper lubrication, or because the spring is too tight, the spring may drive a pin ahead of the trailing edge of the drive unit recess. As a result, a pin may advance and prematurely drop into the next recess or lodge at a corner of a recess. Still another problem with the improper advancement of pins is that a pin may enter a recess in a cocked position; or only one pin will seat in a recess. Consequently, there is uneven loading during the power stroke, and some pins may crack or imbed into the corner of the recess.
In order to achieve proper torque output in the smallest size wrench (6 pins), at least two pins must be properly seated in the rachet during the power stroke. In larger wrenches, between two and twelve pins must be properly seated, depending on the size of the wrench, to achieve proper torque output and lead distribution. If fewer pins than are necessary for proper torque output are seated in the recesses, serious problems are encountered. The pins that are properly seated will be overloaded and may be damaged, thereby necessitating expensive replacement and repair. Also the pins which have not been seated, i.e., which have been hung up and have not properly advanced, may also be damaged.
During the reverse ratcheting stroke, the operator of a wrench of the type under discussion, will hear a "click" sound indicating that the pins have been seated in the recess and that the power stroke may be applied. Unfortunately, often that "click" sound is only one pin dropping into a recess, or less than the desired number of pins. If this condition occurs, the problems discussed above will result.